JPH0617376B2 - Method for controlling product emissions from monomer vapor phase polymerization in a horizontal stirred bed reactor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to the production of polymers and copolymers, and more specifically, vapor phase polymerizing a polymerizable monomer or mixture of monomers to produce a normally solid polymeric material. It is about things. Specifically, the present invention is preferably primarily isobaric using a high yield catalyst and optional cocatalyst in a horizontal, quench, stirred bed reactor that primarily circulates all reactor off-gas. The present invention is directed to a method and apparatus for controlling polymer product withdrawal after polymerizing a monomer or mixture from the vapor phase by the method of.

One of the problems with solution or slurry polymerization of monomers is the investment cost required in the production of polymer products. Monomer polymerization using the vapor phase method can be considerably more economical if some of the problems inherent in it can be solved. They perform polymerization in a thermally controlled manner to avoid hot spots, maintain proper product particle size distribution, and are highly sensitive to poisoning at high yields. Reducing the amount of make-up material presented as catalyst per amount of product formed when using the catalyst to a minimum. Another problem with certain catalyst combinations is the narrow molecular weight distribution of the products formed with these catalysts.

U.S. Pat.Nos. 3,965,083, 3,971,768, 4,101,289
No. 4,129,701 (assigned to the assignee of the present patent application) uses essentially all reactor off-gas circulation and quench stirred bed mode of operation, which is essentially isobaric for polymerizable monomers. Discloses a horizontal reactor for selective vapor phase polymerization. The term vapor phase process or vapor phase reactor means a process or reactor in which the monomer or monomers are vapor or gas under the conditions in which they predominate in the reactor.

The reactor may have one or more than one polymerization zone, preferably there is at least two zones separated from each other by weirs or other appropriately shaped barriers, and there is significant space between those zones. Prevent backmixing. Each zone is individually controlled with respect to polymerization temperature and polymer production rate,
It allows for easier production of polymeric products with controlled broadening molecular weight and particle size.

The reactor introduces the catalyst components and quenching liquid into the polymerization zone directly above and in a stirred subfluidized bed of polymer formed from the monomer polymerization from the gas phase. The catalyst components and quench liquid can be introduced into the multi-zone reactor at different rates to different zones of the reactor to provide individual control of polymerization temperature and polymer production rate in the various zones. The reactor introduces most or all of the monomers or mixtures thereof and optional hydrogen below the polymer bed. Polymer solids are continuously withdrawn by passing through a withdrawal barrier, typically at one end of the reactor, into an withdrawal vessel.

Preferably, the reactor offgas is withdrawn from the offgas as much as possible of the entrained polymer particles along the reactor top. The reactor offgas is then sent to a separation zone where the quenching liquid is separated, at least in part, from the monomer and hydrogen, if used, along with some of the polymer particles and catalyst components, and the monomer and hydrogen. Is then circulated to the inlets that are spaced along the various polymerization zones of the reactor and located predominantly or wholly below the polymer bed surface. A portion of the quench liquid further containing polymer particles is withdrawn from the separator and the majority is returned to the inlets spaced along the top of the reactor. A small portion of this quench liquid is purified from the polymer fines and catalyst components and fed into the catalyst make-up zone for the catalyst diluent,
No new quench liquid has to be introduced for that purpose.

U.S. Pat.Nos. 3,965,083, 3,971,768, 4,101,289
, And 4,129,710, solve most or all of the above problems associated with solution or slurry polymerization, and provide significant economic benefits through savings in energy consumption, raw materials, and investment costs. Is getting
However, known systems for removing polymer products from reactors have resulted in significant reactor downtime and high maintenance costs.

Generally, as described above, the polymer is continuously withdrawn as particulates by passing through the withdrawal barrier at one end of the reactor and into the withdrawal vessel. According to one known system, the level of the polymer bed (height) is maintained at the level of the opening in the retaining weir at the outlet end of the reactor. The polymer overflow spills into the withdrawal zone and is intermittently withdrawn as granules through a double ball valve lock chamber attached to the reactor outlet. This known system consists of a manual shut-off ball valve, an automatic inlet ball valve, a blow case and a discharge ball valve. To expel the product, the inlet ball valve opens for a specified time, thereby filling the blow case with powder. After closing the inlet ball valve, the discharge ball valve is then opened, which discharges the powder from the blow case through a pressure increase to the powder separating drum.

The following problems have been experienced with known systems. The inlet ball valve often condenses during the cycle, thereby causing blockage of downstream discharge elements such as the discharge ball valve. Repair usually requires interruption of reactor operation. This is because the shut-off ball valve is often set in the open state. When the discharge ball valve is clogged with polymer, powder accumulates in the blow case. If not properly cooled,
The heat of reaction melts the powder, thereby producing a molten mass of polymer that causes the blow case to become blocked. Since the reactor cannot be shut off reliably, a shutdown of the reactor must be performed whenever the discharge ball valve or blow case becomes clogged with polymer. Furthermore, in the known system, the particulates flow through openings in the retaining weir into the removal zone and into the blow case. Since the powder seal cannot be maintained above the exhaust ball valve, a large amount of monomer gas exits with the polymer product, thereby creating excessive gas blowby.
This causes monomer loss and at the same time causes high pressure in the powder separation drum. In one aspect, the present invention provides a solution to these operational problems.

Moreover, the reactor is particularly adapted for use with a catalyst, which has a sufficiently high polymerization yield that it is not necessary to remove catalyst residues from the polymer product during the polymer finishing process. However, the quality of the products produced in a horizontal vapor phase polymerization stirred bed reactor is not necessarily equal to that of the slurry process. This is due to the catalyst residue remaining in the gas phase product. The amount of residual catalyst can be reduced by two techniques. Development of improved high-yield catalysts that are outside the scope of the present invention; and / or either by extending the reaction time and thereby reducing polymer output or by increasing the effective reactor volume. Increase in the residence time of the reactor. Traditionally, the effective reactor volume and thus residence time, as disclosed in U.S. Pat. Nos. 3,965,083, 3,971,768, 4,101,289, and 4,129,701, have been limited by weir height. Changing the polymer bed level to increase the residence time requires replacing the weir, which is economically impossible. In another aspect, the present invention provides a solution to the problem of controlling residence time without reduction of polymer production or replacement of weirs.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for controlling product emission from a horizontal vapor phase polymerization stirred bed reactor. According to the present invention, the method of discharging the polymer product in powder form from the withdrawal end of the horizontal vapor phase polymerization stirred bed reactor comprises: (a) a powdered product polymer when the reactor is operating in steady state. Is set to maintain the powder level above the outlet at the outlet end of the reactor;
(b) actuating the discharge device of the discharge zone at a set rate to discharge the powdered product polymer from the discharge port below the powder level; This allows
The advantage is that gas blow-by is reduced.

According to another aspect of the present invention, a method of discharging a polymer product in powder form from the withdrawal end of a horizontal vapor phase polymerization stirred bed reactor comprises: (a) operating the reactor in a steady state When the powder level is kept above the outlet at the take-out end, the level of powdered polymerized monomer is sensed, and the bed level correlates with the force required to agitate the polymerized monomer. The steps consist of operating the device in response to sensing bed level to remove powdered polymerized monomer from the outlet to maintain a powder level above the outlet. This offers the advantage of reducing gas blow-by. Preferably, the agitator drive motor load is correlated with the bed level so that the bed level is controlled by sensing the motor load and discharging polymer to keep the current drawn by the motor at a preselected value. The polymer bed level can be controlled in response to the amperage signal of the stirrer drive motor, which allows the bed level to be controlled at any desired height. The agitator drive motor draws a peak power load when the agitator is activated in a non-fluidized powder bed. The height of the weir is preferably set such that the resistance created by the stationary powder bed is approximately equal to that obtained from the stirrer drive motor. When the polymer bed is fluidized, the agitator drive motor power requirement is greatly reduced, and the excess motor power alters the fluid bed polymer level above the weir,
It can be used thereby to control the residence time. The working volume in the reactor can be increased over what is heretofore permitted, thereby significantly increasing catalyst yield and reducing catalyst residues in the product. Preferably, in accordance with the present invention, the polymerizable monomers or mixtures thereof are provided with a drain valve means capable of sealing the reactor when required followed by an automatic drain ball valve means for controlling the discharge of the product from the reactor. By a gas phase, essentially isobaric, polymerization process using a reactor with quenching in a horizontal stirred bed, essentially all reaction offgas circulation type, with a discharge device of the withdrawal zone consisting of; The catalyst and the optional co-catalyst can be added economically and highly efficiently to the polymeric material.

One embodiment of the apparatus according to the invention for vapor phase polymerizing at least one polymerizable monomer comprises: (a) mounting a stirrer inside the reactor and extending a short distance from its inner surface. Is a horizontal reactor containing a centrally located drive shaft extending longitudinally therethrough and divided into at least two zones by barrier means to control the movement of polymerized monomers between the zones. A reactor; (b) drive means for the drive shaft; (c) at least one reactor off-gas outlet along the top section of the reactor;
(d) at least one gas circulation input along the bottom zone of the reactor; at least one catalyst addition inlet along the reactor; (f) introduction of quench liquid into the zone of the reactor. A plurality of quenching liquid inlets spaced along the reactor so that: (g) along the bottom section of the reactor near one end of the reactor, the polymerized monomer is placed in the reactor. Discharge means for the polymerized monomer for controlling the discharge of the polymerized monomer from the reactor when not sealed by the drain valve means from the reactor. Automatic drain ball valve means (2) in series with drain valve means (1) for selectively sealing the reactor, the drive means preferably being an electric motor, and the automatic drain ball valve means (2) A Is actuated by a pair indicator control circuit, the circuit senses the load on the motor that drives the reactor agitator.

The present invention provides advantages over known horizontal vapor phase polymerization stirred bed reactor discharge systems. Their advantage is to control the powder level above the outlet, thereby improving the monomer yield based on loss reduction, utilizing more reactor volume, thereby increasing catalyst yield and maintenance costs. Lower
Includes the ability to obtain higher operational efficiency based on reduced work interruptions.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 shows one embodiment of a predominantly isobaric polymerization process with predominantly total reactor off-gas circulation which is useful in explaining the present invention.

FIG. 2 is a longitudinal view of one embodiment of the reactor described herein.

FIG. 3 shows a cross section of this reactor along line 3-3 in FIG.

FIG. 4 shows a set of yield curves as a function of residence time for polypropylene polymerization with various catalysts in this type of reactor.

GENERAL DESCRIPTION The methods and apparatus described herein include ethene, propene, 4-methyl-pentene-1, butene-1, vinyl chloride, butadiene, styrene, PET, and mixtures of these monomers, below the softening point of the polymeric form. Can be applied to the polymerization of polymerizable monomers that can be polymerized in. Particularly suitable is the polymerization of ethene and propene.

According to the present invention there is provided a process and a reactor for economically and efficiently converting a polymerizable monomer or mixture thereof into a polymeric material in the gas phase, mainly in an isobaric polymerization process, which reactor is a stirred bed. Is a quenching type horizontal reactor, which mainly has a whole reactor off-gas circulation capable of multiple temperature operations. The method and reactor are subfluidized by a horizontal array of paddles connected to a longitudinally aligned drive shaft that is typically located in the center of the reactor.
fluidized) mechanical agitation of the polymer and dividing the reactor into polymerization zones separated from each other, preferably by suitable barriers such as weirs, these zones being characterized by the rate of polymer formation and the polymerization temperature and if desired. For example, the reactor gas partial pressure can be controlled individually. The present invention provides a discharge method and apparatus at the outlet end of this reactor. This discharge device consists of a drain valve followed by an automatic discharge ball valve. The purpose of the drain valve is to seal the reactor whenever necessary. The function of the automatic discharge ball valve is to control the polymer bed level in the reactor by adjusting the powder discharge rate. During operation, the drain valve is held open while the self-draining ball valve functions to control the polymer bed level, preferably a control circuit, preferably a stirrer drive motor load circuit, or in another embodiment. Turn off the timer circuit.

The method of using the reactor of the present invention is shown in detail in FIG. FIG. 1 is roughly divided into two zones, namely the reactor zone, generally indicated by numeral 100, and the reactor offgas treatment (separation) and catalyst make-up, generally indicated by numeral 200. Area.

As shown in FIG. 1, the reaction volume of the horizontal polymerization reactor 101 has several mechanical stirring zones 167, 169, 171, and 173.
To provide the possibility of operating different sections of the reactor at different temperatures and / or different polymer production rates. Polymerization occurs in reaction zones 167, 169, 171, and 173 to form a polymer bed distributed throughout reactor 101, and the polymerization temperature in each of these zones is mechanically agitated, spaced along the bottom of the reactor. Entrance 175,
Controlled differential introduction of gas circulation into each zone through 177,179 and 181, and quench liquid inlets 153,155,157 and 15 spaced along the reactor top.
9 and the introduction of the inert quenching liquid and the catalyst components into the zones at various rates through the catalyst inlets 123, 125, 127 and 129 can be individually controlled.

Reactor offgas is withdrawn through outlets 183, 185, 187 and 189. Some harmful amount of polymer granules in reactor 1
As such, they may be removed by using traps, filters, settler, cyclones or scrubbers or combinations thereof prior to transferring the reactor offgas to the reactor offgas treatment and catalyst make-up area 200. It is advantageous to do

Polymer solids are produced in each of the mechanically stirred reaction zones 167, 169, 171, and 173. On the basis of such continuous production of polymer, that amount of polymer product is constantly sent to the outlet end 103 of the reactor 101.

In general, the most useful catalysts are those that are highly active and give high catalyst yields. Included within this group are cocatalysts and transition metal compound-based catalysts composed of organometallic compounds of Groups 1A, IIA, and IIIA of the Periodic Table. Aluminum alkyl compound cocatalysts are particularly preferred and may be alkylaluminum halides such as trialkylaluminium or dialkylaluminium chloride. The transition metal catalyst can be a Group IV or V metal compound such as a compound of titanium or vanadium, a Group VI compound such as an oxide of chromium or molybdenum, or a magnesium-based support or alumina, silica. Alternatively, it may be one of the above catalysts supported on a carrier such as silica-alumina.

The preferred catalysts and cocatalysts are high yield catalysts. High yield refers to catalysts and cocatalysts that do not require removal of their residue from the polymer product of the process.

A preferred catalyst and cocatalyst for ethene polymerization is a trialkylaluminum cocatalyst with a catalyst that is a titanium compound supported on a magnesium-based support or chromium oxide supported on alumina-silica, or a combination thereof. For propene polymerization, it is preferred to use a dialkylaluminum chloride cocatalyst and a catalyst that is active titanium trichloride. However, the methods and reactors described herein are not meant to be limited to the catalysts and cocatalysts used, except that they work best with high yield catalysts.

The quenching liquid used for temperature control is an easily volatilizable liquid that can be sprayed onto the surface of the polymer bed and conduct heat from the bed by evaporation, and thus the monomer being polymerized, during polymerization. It should be inert to the catalyst components used and should have as high a heat of vaporization as is compatible with the volatility of the quenching liquid in the reactor at the polymerization temperature. Generally, alkanes such as propane, butane, pentane, or hexane or mixtures of these with close boiling points can be used. The preferred quenching liquid for ethene is isobutane or isopentane. If the monomer to be polymerized is readily condensable, for example propane, the quench liquid can be a liquefied monomer or a mixture of a liquefied monomer and an additional quench liquid.

The quench liquid addition rate is low enough to keep the polymer bed dry, i.e., the partial pressure of the quench liquid vapor below its dew point, and yet sufficient to obtain the maximum cooling effect of the quench liquid. Great speed. Generally, quench liquids carry away 50% or more of the heat of polymerization. In the case of propene polymerization, it is desirable that 90% or more of the heat of polymerization be removed by a quenching liquid. At a polymerization temperature of 200 ° F. (93 ° C.) in ethene polymerization, preferably 70% or more of the heat of polymerization is removed with isobutane and 50% or more of the heat is removed with isopentene.

Catalysts dissolved or slurried in a circulating quench liquid are placed on the surface of the polymer bed in various reaction zones 167,169,171 and 1
Inlet 123,12 in FIG. 1 in at least one of 73
It is advantageous to introduce through 5,127 and 129. The similarly arranged inlets 153, 155, 157 and 159 allow the circulating quenching liquid, which may contain a catalyst, to pass into individual reaction zones 167,
Used to introduce above the polymer bed in 169,171 and 173. However, depending on the nature of the catalyst, co-catalyst, monomer to be polymerized, the catalyst and / or co-catalyst can be sprayed into the reactor neat or in a non-polymerizable vehicle or can be introduced separately. it can. Furthermore, for some monomers, catalyst and cocatalyst can be added to make-up zone 145 and can be added together to reactor 101.

The catalyst inlet and the quenching liquid inlet can be concentrically created to spray the catalyst and quenching liquid into the reactor 101 and onto the polymer bed surface in a manner that more evenly distributes the catalyst to the bed surface. . However, the catalyst inlet and quench liquid inlet can be made separately to introduce catalyst and quench liquid separately into the polymer bed.

The circulation system and the reactor are designed such that they are essentially isobaric. That is, there is nothing more than pressure fluctuations during normal work. Preferably, the pressure fluctuations in the reactor 101 and the circulation system are ± 25 psig (1.7 kg / cm ² ) or less, more preferably ± 10 psig (0.7 kg / cm ² ) or less.

As shown in FIG. 1, the reactor off-gas is sent to a washing tower 133 through a pipe 131, and at least a part of the quenching liquid component of the off-gas, polymer fine particles, and some of the catalyst components include a polymerizable monomer and a polymerizable monomer. It is removed from hydrogen when used. The polymerizable monomers and hydrogen along with some quench liquid vapor are added to the reactor 101 from the top of the scrubbing column 133, preferably through heat converter 160 and separator 161, to additionally condense the quench liquid. It will be returned later. Alternatively, the monomer and hydrogen are transferred from the wash tower 133 to reactor 1
The heat exchanger 160 and the separator 161 can be returned to 01 without passing through them. Individual reaction zones 167,169,171 and 1
It is introduced into 73 via inlets 175, 177, 179 and 181. The amount of vapor recycle can be controlled by valves 191, 193, 195 and 197 so that the polymer bed can be kept in a sub-fluid state. The quench liquid from separator 161 is essentially free of polymer particulates and catalyst components and is suitable for use in catalyst make-up zone 145.

The liquid for quenching separated from the reactor off-gas is pump 135
To the heat exchanger 154. This quenching liquid is cooled by the heat exchanger 154, and most of it is returned to the top of the washing tower 133 via the pipe 138. A small portion of the quenching liquid passes through the pipe 137, the heat exchanger 143, the pump 139, and the quenching liquid circulation pipe 151, and the quenching liquid inlets 153, 155,
Some of the monomer that is returned to 157 and 159 and carried with it by offgas into the scrubbing tower 133,
Carries hydrogen, catalyst and polymer granules. The supply of the quenching liquid is added through the pipe 140. Separator 1 is a small portion of the quenching liquid that is essentially free of polymer particles and catalyst components.
It is taken out of 61 and sent to the catalyst replenishment zone 145 through the pipe 134 and the pump 136 for the purpose of catalyst replenishment. If a co-catalyst is used, the supplemental co-catalyst is added to the catalyst replenishment zone 145 or piped into the circulating quench liquid stream.
It can be injected directly via 7 or added directly into the reactor 101 in a non-polymerizable vehicle.

Polymerization at the catalyst make-up zone 145 or the associated piping 149 and the inlets and inlets 123, 125, 127 and 129 causes serious blockage problems and can be controlled by keeping the co-catalyst concentration in the catalyst make-up zone 145 below a certain value, which is used. It depends on the nature of the catalyst and cocatalyst and the monomers to be polymerized. The replenishment co-catalyst is placed in the catalyst replenishment zone 145.
When added to, the polymerization in related piping 149 is prevented from occurring by cooling the make-up zone or reducing the residence time of the catalyst components therein. Furthermore, the make-up quench liquid from line 147 can be used in the catalyst make-up zone 145 instead of into the circulating quench liquid to prevent polymerization of the monomer in the catalyst make-up zone.

A valve 199 is provided in the catalyst make-up zone bypass line to more easily change the catalyst concentration in the catalyst make-up introduced into the reactor 101. The particles of polymer produced in the reactor 101 are pipes 123, 125, 127 and 129.
It has been discovered that this can be beneficially altered by varying the concentration of the catalyst being introduced through. Furthermore, it is advantageous to change the catalyst concentration in the catalyst replenishment zone 145, or additionally and separately, the quench liquid into the catalyst line 149 via valve 199, where the catalyst enters the inlet 123,
It has been discovered that it is advantageous to introduce immediately before the position entering 125, 127 and 129. The supplementary catalyst is added through the pipe 142.

The weir, if used, is attached to the drive shaft 104 with a slip ring or reactor 101.
Can be fixed to the walls of the weir and is advantageously aligned so that the top of the weir aligns with the orientation of the polymer bed during stirring. This allows spillage along the entire length of the top of each weir. However, the tops of the weirs can be arranged horizontally if desired. Other types of barriers are used instead of weirs and reaction zones
Violent backmixing between 167, 169, 171, and 173 can be prevented. For example, a thin walled barrier attached to the drive shaft 104 can be used, which fills the reactor cross section and has one or more holes in it.

The polymer solids that accumulate in reactor 101 move across the length of reactor 101 essentially due to polymer accumulation in the reactor bed and not due to mechanical agitation. This situation is ensured by the form of the paddle used, which form provides stirring but not backward or forward movement of the polymer bed.
Particles in the polymer bed proximate to the withdrawal end 103 are washed away by the agitation to the withdrawal zone. The ejection zone discharge device according to the invention is generally indicated by the numeral 201 in FIG.

The polymer is melted without substantial pressure drop; the solid is melted, the resulting melted polymer is treated with killing substances and additives, devolatilized while still in the molten state, and then processed into commercial-sized products. Take it out in a bursting manner. Preferably, the polymer solids are removed according to the invention, treated with additives and melt-extruded.

Description of the Preferred Embodiments FIG. 2 shows reactor 101 in detail, reactor 10
The inside of 1 is a reaction zone 167,169,171 which can be controlled individually.
And 173, and weirs 110, 112 and 11 are connected to each other.
Separated by 4, these weirs preferably extend upwards somewhat above the middle of the reactor at a height equal to the surface of the non-fluidized polymer bed. In a preferred embodiment, the weir
110, 112 and 114 are constructed at a height such that the polymer bed fills about half the reactor volume. As the solid polymer exceeds the height of the weir, it falls into the adjacent areas 167, 169, 171, and 173 and migrates toward the withdrawal end 103.

When it is desired to operate with two or more gas compositions (different hydrogen concentrations) as well as different zone temperatures, all zone barriers divide reactor 101 into chambers of different gas compositions. Same as above, except for one or more than one split structure. The split structure in such a case comprises a thin-walled barrier that expands upwards to occupy the cross-section of the reactor 101 and which is located below the polymer bed level and contains openings for moving polymer solids. Gas intermixing between chambers is controlled thereby. When operating in such a variable gas composition mode, these separate chambers preferably have separate reactor offgas cycle and return facilities and separate hydrogen and monomer replenishment facilities. Generally, these split structures prevent excessive intermixing of vapor between the individual chambers. However, in one mode of multiple hydrogen operation,
The vapors are supplied from a room with a small amount of hydrogen to a room with a large amount of hydrogen, and the replenishment monomer is mainly supplied to a room with a small amount of hydrogen
And, by supplementing the hydrogen supply mainly to the hydrogen-rich room, the vapors are mixed intentionally. Alternatively, two or more than two separate reactors can be used in series, if desired, to operate two or more gas compositions.

A drive shaft 104 extending vertically in the reactor is installed inside the reactor 101, and a drive shaft 104 extending in the lateral direction from the drive shaft 104 forms a gap close to the inner wall of the reactor.
106, 108, 120, 122 and 132 are installed to ensure proper polymer bed mixing at the reactor walls.
These paddles are preferably flat to maximize polymer bed agitation for a given rotational speed, and preferably use two paddles per impeller. The width of the paddle is such that about 4 to about 12 impellers (8 to 24 paddles) are present in the reaction zone about 3 feet in length. The paddles on the adjacent impellers are oriented at about 90 °. These paddles are configured to minimize the forward or backward motion of the polymer bed during agitation, and the agitator drive motor 102 causes the reactor 101
It is driven at such a speed that it slowly overturns the entire floor contained inside it in a regulated manner. Agitation drive motor 102 is preferably an electric motor. The speed at which the impeller spins is preferably fast enough to provide the desired heat and mass transfer between liquids, solids and gases,
However, it is preferred that the particulate portion of the polymer bed is not so fast that it is dumped in bulk into the space above the bed. That is, the rate is typically about 5 to about 30 RPM to maintain polymer bed integrity.

The reactor 101 is provided with a plurality of catalyst inlets and a quenching liquid inlet.
And one or more catalysts and an inlet for quenching liquid to each reaction zone 167, 169,
Available for 171 and 173. The catalyst and quench liquid inlets are typically designed to be distributed at about the same location on top of the stirred polymer bed. Such introduction of catalyst and quenching liquid in combination with gentle agitation provides a more homogenous polymerization and prevents localized melting in the polymer bed, thus reducing the number of melt clogging of the polymer formed and reducing trouble. Gives less reactor performance. In one mode of carrying out the polymerization in reactor 101, it is advantageous to controllably add the catalyst components and quench liquid into the various zones, for example by valves. Separately controlled additions of this type into reaction zones 167, 169, 171, and 173 serve to provide separate control of polymerization temperature and polymer production rate between each zone, altering the molecular weight and particle size distribution of the polymer and Can be used to control.

Catalysts being introduced into various reaction zones 167, 169, 171, and 173, if one or more polymerization temperatures are kept at different values in the other zones (dual-temperature operation or multi-temperature operation) It is advantageous to change the concentration of any or all of the components. The particle size distribution and the molecular weight distribution are thereby influenced advantageously. This can be achieved by feeding the catalyst inlets in different zones individually. Even at single temperature operation,
It may be advantageous to feed one or more of the reaction zones 167, 169, 171, and 173 with a different concentration of catalyst than the catalyst components being introduced into the other zones.

The overall temperature range for the polymerization will depend on the particular monomer being polymerized and the desired commercial product. Generally, the temperature range of use will vary from about 40 ° C. to near the softening temperature of the polymer bed. The total polymerization pressure is the polymerizable monomer pressure,
Consists of the pressure of the vaporized quenching liquid, and the hydrogen pressure, if used, such total pressure typically can vary from about atmospheric pressure to about 600 psig (42 Kg / cm ² ). The individual partial pressures of the components that make up this total pressure are the rates at which polymerization occurs,
Determine the molecular weight and molecular weight distribution of the polymer produced.

The vapor cycle containing the polymerizable monomer or monomers and hydrogen, if used, is introduced through the vapor circulation line 156 to the vapor cycle inlets 175, 177, 179 and 181 at a rate designed to prevent fluidization of the polymer bed. This vapor recycle gas is used in the individual reaction zones 167, 169, 171,
The speeds introduced into the three valves are 191, 193, 195 and 197.
And such control can be used to help alter the area polymerization rate and, if necessary, the polymer polymerization rate. The insert end plates inserted in the reactor 101 for the purpose of mechanical construction are shown at 124 and 126.

In FIG. 3, a drawing of the reactor is shown along line 3-3 in FIG. FIG. 3 shows the 90 ° orientation of the paddles 120 and 132 on the adjacent impeller at the exit end 103. Further, FIG. 3 shows the orientation of the polymer bed in the paddle 114 and the reactor and the direction of movement of the paddle with respect to bed orientation.

As shown in FIG. 2, the discharge device 201 in the discharge zone basically comprises the discharge end 103 of the reactor 101.
Drain valve 20 connected to outlet 204 in
Equipped with 3. The drain valve 203 is preferably a conventional valve having a valve stem (valve stem) that can be selectively actuated between a closed position and an open position. In the closed position, the valve stem has a valve seat. Resting on the (valve seat), thereby closing the reactor 101, while in the open position the valve stem separates from the valve seat, whereby the polymer in powder form leaves the outlet end 103 of the reactor. Flowing. Preferably, the level of powdered polymer is drain valve 2
03 is maintained above the outlet 204 at the location where it is connected to the outlet end 103 of the reactor 101, thereby reducing gas leakage. It has been found that it is more important to use the drain valve 203 than the ball valves used previously, because the drain valve is less likely to be closed with the molten polymer than the ball valve. This is because the area near the valve seat of the drain valve 203 is more likely than the throat of the ball valve, and thus the molten polymer will clog the valve even in the presence of molten polymer, thereby condensing with the valve open. Because it is small. Drain valve 20
3 can be, for example, a 4-inch motor operated valve available from Strathman, Houston, Texas.

The discharge device 201 is basically also an automatic discharge ball valve 20.
Including 5. This automatic discharge ball valve 205 is the drain valve 20.
When connected to 3 and the drain valve is open, powdered polymer is delivered to the ball valve. The self-draining ball valve can be selectively actuated between a closed position where the flow of powdered polymer from the drain valve 203 is blocked and an open position where the powdered polymer is allowed to flow. The automatic ejection ball valve 205 can be, for example, a 3-inch automatic ball valve manufactured by WKM of Houston, Texas. The powdery polymer flowing from the automatic discharge ball valve 205 is passed through a pipe 207 to a powder separation drum or other product treatment device 2
Enter 11.

Preferably, as shown in FIG. 2, the ball valve 209 is inserted between the drain valve 203 and the automatic discharge ball valve 205. Ball valve 209 serves as a safety valve for selectively sealing automatic discharge ball valve 205 from drain valve 203. Further, another ball valve 213 is inserted between the automatic discharge ball valve 205 and the pipe 207, and the automatic discharge device 20 is provided.
1 serves as a safety valve that selectively seals 1 from the downstream product processor 211. Both safety valves 209 and 213 can be actuated between open and closed positions to pass and block the flow of powdered polymer, respectively, but are in the open position during normal operation of the reactor 101.

The ejection device 201 is characterized by the following features. The conventionally used shut-off ball valve is replaced by the drain valve 203. The drain valve 203 pushes the powder clogging out of the way and can seal the reactor in a reliable manner. In addition, the previously used automatic inlet ball valve is eliminated. Also, the blow case is removed, thereby removing any blind spots where the polymer accumulates and melts. Finally, the powder level can be kept above the outlet 204. The ejection device 201 has no blind spot space. This minimizes gas blow-by and the associated loss of monomer.

Ejection device 201 offers several advantages over previously known ejection systems. These advantages include reduced maintenance costs,
Includes improved work factors based on reduced downtime and improved monomer yields due to reduced monomer losses.

The following examples are given with respect to the features and advantages of the ejection device 201 as compared to previously known ejection systems.

Example 1 A method using two parallel gas phase polymerization stirred bed reactors as described herein was carried out under the following process conditions: Reactor dimensions ... 8 feet (2.4 m) diameter per unit, 44 feet (13.2m) long Monomer: Propylene (99.7 mol%) Monomer feed rate: 16.600 lbs / hr (7.470 Kg / hr) Propane (C ₃ H ₈ ) feed rate: 50 per reactor lb/
Hour (22.5 Kg / hr) Hexane (C ₆ H ₁₄ ) feed rate …… 63 lbs / hr (28.4 Kg / hr) catalyst …… Titanium trichloride (Ticl ₃ ) catalyst feed rate …… 1.88 per reactor Pound / hour (0.84Kg
/ H) Diethylaluminum-chloride Feed rate: 6.58 lbs / h per reactor (3.0 kg / h)
Hydrogen sulfide (H ₂ S) feed rate: 0.01 lb / hr (0.0045 Kg / hr) per reactor 2,4,6-collidine feed rate: 0.07 lb / hr (0.032 Kg / hr) per reactor Hydrogen (H ₂ ) supply rate: 1.0 lb / hr (0.45 Kg / hr) per reactor Temperature: 160 ° F (71 ° C) Pressure: 300 psig (21 Kg / cm ² ) Polypropylene Apparent specific gravity of powder ...... 30 pounds / cubic foot (0.48g / cm ³ ) powder holding per reactor …… 50% level, 30,000 pounds (13,500Kg) production rate …… 15,075 pounds / hour (6,783Kg / hour) The polymer product produced by each was discharged to the same product processor 211 according to the present invention.

The installation of the horizontal gas phase polymerization stirred bed reactor discharge device of the present invention reduced maintenance and work interruption costs over 9 months. 3 less interruptions to reactor work over the same period,
It resulted in a 45,000 lb (20,300 Kg) reduction in propylene flare loss and a 90,000 lb (40,500 Kg) reduction in rejects. In addition, in an attempt to study monomer loss, the previously described previously known discharge systems used previously were tested and the results showed that maintaining powder levels in the unloading zone reduced propylene monomer loss. Under the above process conditions, the propylene concentration in the fluidized bed catalyst deactivator contained in the product treatment apparatus 211 was reduced from 38 to 29 mol%. This is 9
There was a substantial monomer savings for the months. The ability to raise the powder level above the outlet also lowered the pressure in the powder separation drum contained in the product processor 211 from 8 to 3 psing (0.56 to 0.21 Kg / cm ² ).

A preferred embodiment of the discharge device of the invention seen from the above examples relates to the reduction of maintenance costs, work interruptions and material losses when operating in a manner in which the weir controls the height of the polymer bed, In particular, the ejector will bring the powder level to the reactor 101
Above the outlet 204, thereby avoiding gas blow-by and thus reducing monomer loss. To maintain a sufficient polymer powder seal above the outlet 204, the timer circuit 215 shown in FIG. 2 can be used to control the intermittent ejection of polymer from the reactor 101. The timer circuit 215 is connected to an actuator 217 that controls opening and closing of the automatic discharge ball valve 205. After the reaction in the reactor 101 reaches a steady state, the timer circuit 215 is kept sufficiently slow so that the automatic discharge ball valve 205 keeps the powder level above the discharge port 204 and avoid backup in the reactor 101. Set to cycle at a sufficiently fast rate. The powder level above outlet 204 maintains a powder seal to mitigate gas blow-by problems.

According to the present invention, the discharge device 201 is used to discharge the discharge port 20.
4 not only can the powder level be maintained above, but the polymer bed level throughout the reactor 101 can be controlled by an evacuation device to increase the effective volume of the reactor and thus the residence time of the polymer in the reactor, thereby producing The product quality can be improved. That is, the residence time can be increased without reducing the polymer output or replacing the weir.

The automatic drain ball valve can be controlled by timer circuit 215 and actuator 217 in a similar manner as described above to control the polymer bed level throughout reactor 101. That is, after the reaction in reactor 101 reaches a steady state, timer circuit 215 is set to maintain the polymer bed level throughout the reactor at the required level to provide the desired residence time. However, in the preferred embodiment where the polymer bed level is controlled throughout the reactor 101 to achieve the desired residence time, the actuation valve 217 for the automatic drain ball valve 205 is an ampere indicator connected to the stirrer drive motor 102. Total control circuit 219
Controlled by.

The discharge device 201, which includes a drain valve 203 followed by an automatic discharge ball valve 205, operates in the presence of some powder level. Ampere indicator controller circuit 2
19 uses a correlation based on polymer bed level and correlates the agitator drive motor ampere drawer with a bed level to control the operation of the automatic drain ball valve 205. Since the reactor 101 is in a steady state, the actuator 217 operates the automatic discharge ball valve 205 so that the current drawn by the agitator drive motor-102 is set in the ampere indicator control circuit 219. It is set when the polymer will only be discharged at least at equal times, and this condition occurs when the polymer bed level is exceeded.

In operation, the reactor 101 is started with the polymer bed level equal to the weir height. Once the polymer bed is once fluidized and the reaction is running, the desired residence time is set by increasing the amperage control setting to give the desired bed level. That is, the excess power available from the agitator drive motor 102 when the polymer bed is once fluidized is advantageously used to regulate the bed level. The preferred polymer bed level control method of the present invention lowers the bed level during the start of agitation and then raises the bed level once the reaction has proceeded, which allows reactor 101 to be started up more quickly.

According to the present invention, polymer bed levels can be increased by a factor of two over previously known bed levels, thereby doubling reactor residence time and reducing catalyst residues in the product. Bed level control according to the present invention greatly increases the stretchability of introducing new products into the gas phase process, which are currently limited to slurry processes.

Example II The graph shown in Figure 4 shows 15,075 pounds / hour (6,783 Kg / hour).
Doubling the true residence time in the reactor from 2 hours to 4 hours with respect to the production rate and normal catalytic activity of OH was expected to reduce catalyst residues in the polymer product by 34%. Shows. Actual measurements show a 40% reduction in catalyst residue.

Implementation of the polymer bed level control method of the present invention provides several advantages over previously known constant bed level operations.
Their advantage provides the flexibility of controlling polymer bed levels and residence times as needed to optimize the polymerization process, resulting in higher catalyst yields and less catalyst residue in the product. This includes improving the polymer product quality by enabling and allowing more product grades to be produced by the gas phase process. In addition, the retaining weir included in the known drainage systems previously used to control polymer bed levels can be eliminated.

Although the present invention has been described with reference to the specific embodiments above, it should be understood that they are for illustration purposes only. Many variations, modifications, and variations will be apparent to those of ordinary skill in the art, and it is believed that such variations, modifications, and variations fall within the spirit and scope of the "claims".

[Brief description of drawings]

FIG. 1 illustrates one embodiment of an essentially isobaric polymerization process which utilizes essentially all reactor off-gas circulation useful in explaining the present invention. FIG. 2 is a longitudinal view of one embodiment of the reactor described herein. FIG. 3 is a cross-section of such a reactor along the line 3-3 in FIG. FIG. 4 shows a set of yield curves as a function of residence time for polypropylene polymerizations using various catalysts in this type of reactor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teimi Ale Meir-Texas, USA 77598 Webster Heritage Bay Drive 17223 (72) Inventor Jiyoung Lee Page Texas 77546, USA Friends Wood East Castle Harbour 433 (72) Inventor Michael E. Paul, Texas 77566, United States Lake Jackson Oleander 1021 (56) Reference JP-A 51-86584 (JP, A)

Claims (2)

[Claims] 1. A method for discharging a polymer product in powder form from the outlet end of a horizontal vapor phase polymerization stirred bed reactor; (a) a powder when the reactor is operating in a steady state. The rate at which the shaped polymer is discharged to maintain the powder height (level) above the outlet at the outlet end of the reactor; (b) the powder from the outlet below the powder level. Operating a discharge device in the extraction zone at a set rate to remove the resulting polymer in the form of a gas; a process, thereby reducing gas-blowby. 2. The reactor is divided by at least one barrier into at least two polymerization zones and the velocity is set slow enough to maintain the desired product polymer bed level above the barrier, thereby increasing the residence time. A method according to claim 1, wherein the method is increased.